Friends hello! This time we're gonna
be talking about disc breaks and how to skim them or resurface them when either they warp or their unevenly worn and have groves in, and so on. [Intro Music] [impact wrench noises] let's get started with this then. So
first thing to do is get the disc brake off the car. I'm going to assume that
most people can do this otherwise just look it up. There's like a million
YouTube videos on removing the calipers, changing the pads, changing the discs
and all that. In this case we don't want to change the discs! We want to reuse the
old discs. They are a big chunk of metal, they're almost always cast-iron and it
seems a big waste, just throw them away each time. They're even designed with
resurfacing in mind. it's kind of unfortunate that commercial garages
treat them as disposable items these days, almost changing them as regularly
as the pads themselves, if there's any kind of pitting or grooving the kind of
thing that you could really easily get out in a resurface operation. So I'm going to take you through how to do this. The first thing to do is really wire brush
most of the mess off. Clean them up a bit get the abrasive disc brake
particles off as much as you can. This inside bit's really important to get
clean, because that's what we're going to be mounting to. I had the caliper seize up so the brake pad wasn't
retracting properly and so constantly rubbed on the disc and that caused
overheat, and the disc best to warp slightly. So one of the first things you're going
to need to do is work out if you have enough thickness to resurface the disc.
Do a google or even go to one of the places that does the car part- a
replacement disc - and normally in the stats for it it'll tell you a minimum
thickness. I had a good couple of millimeters or millimeter and a half to play with, which is plenty to resurface the disk. So it is conceivably possible to resurface
the disks in a four jaw chuck using a dial indicator. This is really difficult
though, because to make the surfaces exactly parallel it takes a lot of
fiddling about. This is what I read and that's mirrored my experience. So the
main part of this video is actually going to be making the adaptor- arbour
fixture type thing to mount the disk in the lathe. EEEch. I dont know what kind of pipe it was, but it definitely had a thick layer of gunge in there. Not very nice... The disc break fixture is gonna be made from
that pipe you just saw me turning up and this big scrap lump of steel I'm not
sure exactly what kind of steel it is. It turns rather well. The basic premise
here is that the disk brake will eventually clamp to this Disk of Steel,
which is going to make the fixture and before each time you use the fixture
you'll take a small skim off the plate and that'll ensure complete concentricity.
I've got a small section of high tensile steel 16 millimeter threaded rod that I
want to use for clamping and I'm just turning that down so it fits nicely in
the hole you saw me drilling in that steel disc just a moment ago. [click, click, click of turning dial] The welder is on, you can hear that in the background. I've got my ground clamp here. I'm gonna weld round here first and then flip it over to do the other side. It's on quite a high setting so hopefully the wire will
plunge right in, and we will get good penetration. [loud sparking/welding] The way I'm doing this is with opposing welds to try and minimize the amount of distortion that's gonna be. There's always gonna be some warpage doing a hefty weld like this in such thick material. Going by eye [chuckle] Plonking a weight on top... Here's that pipe you saw me turning earlier. It's got a nice big 45 degree chamfer on it which provides plenty of room for a
deep weld fillet. Again firstly I'm just making some opposing tack welds to hold the
part sturdily and in place. Once I've done that, then I can take my time with some nice inch long sort of seen welds, both inside and outside of that pipe. Mainly
angling the gun so it's going down into the big steel disc as that's the much
more massive of the two. So here it is cooled down and chucked up. The pipes now
chucked in the three jaw and you can see there's a reasonable amount of warpage
occurred during the welding. That's entirely expected when you weld
something like this. The idea now is that that won't move from the three jaw chuck until I finish all four of the brake discs of the van. [Sped up hacksaw noise] [Vacuuming noise] With everything else set I can come to
this ultimate final skim of the clamping surface that will be mating with the
disc break. This is a very fine finishing cut with a sharp new bit of carbide. With that done we're about finished with
the fixture so we can put the first disc on. And it goes on as if mounting onto
the axle of the car - so we want that same surface to meet, and just like when you
put the disc on a car, it's really crucial to make sure there's no foreign
debris in between the two surfaces are being clamped together. So no specks of
rust that can really put it out of alignment and mean that you end up with
unacceptable amount of run out in your final disc. So this doesn't need to be
ridiculously tight because it will be turning in a direction where it would
kind of self tighten anyway but something decent... and then we need to
clock up and check that we've got this on roughly right and it's nice just to
see quite how warped the disc is or how true it's running to that inner surface
that would be meeting on the axle. With an idea of the high and low spots and
the difference between them we can gauge what kind of roughing cuts we need to
take and get started with the actual turning. For this lathe at least, the disc
brakes about at the limit of what it could turn without creating a gap in the
bed and doing all kinds of extra fettling, which probably would make the
project not worth doing. So if you're following along I guess it's best you
check the disc will actually fit on your lathe before starting any of this
project, assuming you have a lathe and you're not just watching out of interest
of course. Once the outsides been turned, we then need to take the finest of skims
off this part of the disc brake. This is the part that the wheel will clamp on to when it's on the car and we need to make this exactly
parallel to the inner surface that we're clamping to and often corrosion means
that it's not so with the finest of skim off that, we can then flip the whole disc
and clamp it back onto our fixture and we know we have the surface completely
parallel and I just verify that by clocking off the.. what is now, back surface, the one that was skimmed before starting even the braking surface on
this side. You're not going to be able to see it, you will have to take my word for it. Yep. So I know that's parallel with that edge which is also parallel with
that face and the back face and that's pretty much got me covered. So I think it probably is important to state the obvious, which is you do need to use a dial indicator to... to confirm that all
the surfaces are parallel and true. With that done this could be taken off and
put on the car now. First though, I'm just gonna quickly rebuild the caliper. This is the
seized one. I'm not going to go into the details of this, but it basically needed
polishing up and all corrosion cleaned off. It seized because the seal had broken and so dirt was getting in there. You can get new seal rebuild kits which
is a good way of doing it, I think because it means you can reuse the the meat of
the caliper. So I really like this whole process because it means you can almost double if not more the lifespan of your typical disc brake. Once you set up and
going with your lathe fixture it's not too time-consuming either. I do feel
though that I should give some words of caution here. If you're not confident
with any of this process, or competent for that matter, then it's probably best
avoided because it really is a safety critical item! I feel a bit foolish just stating the obvious there, but better safe than sorry, I guess. One other thing to
note is that the disc always need redoing in pairs whether that's
replacing or resurfacing. You'd probably notice I didn't use any coolant during
the cutting and that's because it's cast iron so it should self lubricate and
another note on the cast iron is that it can be really abrasive. It creates
very small particles not like turning steel, so it's well worth protecting your
ways and being very vigilant like hoovering up all the dust. Well friends
that's about it, do let me know in the comments below if you found that useful
or if you think it's a load rubbish and you've got a better way of doing it. It'd
be great to hear from you! Thanks for keeping me company and I'll see you next
time!
